USED FUEL DISPOSITION CAMPAIGN Gap Analysis to Support Extended Storage of Used Nuclear Fuel Rev. 0 Prepared for U.S. Department of Energy Used Fuel Disposition Campaign Brady Hanson (PNNL) Halim Alsaed (INL) Christine Stockman (SNL) David Enos (SNL) Ryan Meyer (PNNL) Ken Sorenson (SNL) January 31, 2012 FCRD-USED-2011-000136 Rev. 0 PNNL-20509 USED FUEL DISPOSITION CAMPAIGN Gap Analysis to Support Extended Storage of Used Nuclear Fuel Rev. 0 ii JANUARY 31, 2012 Disclaimer This information was prepared as an account of work sponsored by an agency of the U.S. Government. Neither the U.S. Government nor any agency thereof, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness, of any information, apparatus, product, or process disclosed or represents that its use would not infringe privately owned rights. References herein to any specific commercial product, process, or service by trade name, trade mark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the U.S. Government or any agency thereof. The views and opinions of the authors expressed herein do not necessarily state or reflect those of the U.S. Government or any agency thereof. USED FUEL DISPOSITION CAMPAIGN Gap Analysis to Support Extended Storage of Used Nuclear Fuel Rev. 0 January 31, 2012 iii Reviewed by: Steven C. Marschman (Idaho National Laboratory) Technical Reviewer Ken B. Sorenson (Sandia National Laboratories) Storage and Transportation Control Account Manager Submitted by: Brady Hanson (Pacific Northwest National Laboratory) R&D Investigations Team Lead USED FUEL DISPOSITION CAMPAIGN Gap Analysis to Support Extended Storage of Used Nuclear Fuel Rev. 0 iv January 31, 2012 USED FUEL DISPOSITION CAMPAIGN Gap Analysis to Support Extended Storage of Used Nuclear Fuel Rev. 0 January 31, 2012 v EXECUTIVE SUMMARY This report fulfills the M1 milestone M11UF041401, “Storage R&D Opportunities Report” under Work Package Number FTPN11UF0414. The U.S. Department of Energy Office of Nuclear Energy (DOE-NE), Office of Fuel Cycle Technology, has established the Used Fuel Disposition Campaign (UFDC) to conduct the research and development activities related to storage, transportation, and disposal of used nuclear fuel and high-level radioactive waste. The mission of the UFDC is to identify alternatives and conduct scientific research and technology development to enable storage, transportation and disposal of used nuclear fuel (UNF) and wastes generated by existing and future nuclear fuel cycles. The Storage and Transportation staff within the UFDC are responsible for addressing issues regarding the extended or long-term storage of UNF and its subsequent transportation. The near-term objectives of the Storage and Transportation task are to use a science-based approach to develop the technical bases to support the continued safe and secure storage of UNF for extended periods, subsequent retrieval, and transportation. While both wet and dry storage have been shown to be safe options for storing UNF, the focus of the program is on dry storage at reactor or centralized locations. Although the initial emphasis of the program is on commercial light-water reactor uranium-oxide fuel, DOE-owned research and defense used nuclear fuels as well as alternative and advanced fuel concepts being investigated by the DOE will be addressed later in this program. Because limited information is available on the properties of high burnup fuel (exceeding 45 gigawatt-days per metric tonne of uranium [GWd/MTU]), and because much of the fuel currently discharged from today’s reactors exceeds this burnup threshold, a particular emphasis of this program is on high burnup fuels. Until a disposition pathway, e.g., recycling or geologic disposal, is chosen and implemented, the storage periods for UNF will likely be longer than were originally intended. The ability of the important-to-safety structures, systems, and components (SSCs) to continue to meet safety functions over extended times must be determined and demonstrated. In addition, the ability of these SSCs to meet applicable safety functions when the used nuclear fuel is transported must be ensured. To facilitate all options for disposition and to maintain retrievability and normal back- end operations, it is considered an important objective of this program to evaluate the likelihood that the used nuclear fuel remains undamaged after extended storage. This does not preclude consideration of other options, such as canning of all UNF, from a total systems perspective to determine overall benefit to nuclear waste management. This report documents the initial gap analysis performed to identify data and modeling needs to develop the desired technical bases to enable the extended storage of UNF. For most SSCs important to safety, additional data are required, often because there are limited data on the new materials used in more modern fuels or dry storage cask systems or because the effects of high burnup and extended storage are not fully known. Based upon the importance of the SSC to licensing a dry storage system or an independent spent fuel storage installation (ISFSI), the potential effects of extended storage or high burnup on the degradation mechanism, and a combination of the data needs, regulatory considerations, likelihood of occurrence, the USED FUEL DISPOSITION CAMPAIGN Gap Analysis to Support Extended Storage of Used Nuclear Fuel Rev. 0 vi January 31, 2012 consequence of degradation, the means to remediate the degradation, and the impact of degradation on cost, operations, and future waste management strategies, a research and development (R&D) priority (Low, Medium, or High) is assigned. The R&D priority cannot be higher than the ranking assigned for importance to licensing; obviously, a structure, system, or component ranked of Low importance to licensing does not require a Medium or High priority for R&D. However, a structure, system, or component can be of High importance to licensing, but the R&D needs can be lower depending on the prioritization criteria. The degradation mechanisms identified in this report are limited to those during normal dry storage operations and potential off-normal conditions. Impacts of degradation mechanisms on demonstrating compliance with design basis accidents including those initiated by natural phenomena are not discussed in this report. This report is meant to be a living document that will be updated as additional technical data become available and as policy decisions are implemented. Future revisions will include formulating the technical bases for consideration of accidents and natural phenomena during extended dry storage. In addition, future revisions will compare the gap analysis generated as part of the UFDC with similar analyses developed by the U.S. Nuclear Waste Technical Review Board, the U.S. Nuclear Regulatory Commission, Electric Power Research Institute, and international organizations. A similar gap analysis effort is under way as part of the UFDC to examine the needs to meet transportation requirements. Once the transportation work is completed, the results will be consolidated in a consistent manner in a revision to this report to form a single set of gaps and congruous direction for addressing these gaps to meet applicable storage and transportation requirements. There are several cross-cutting needs for dry storage. These cross-cutting needs are key to detecting, understanding, and evaluating the extent of many of the degradation mechanisms, as well as both determining and validating alternate means of demonstrating compliance with specific regulatory requirements. Table S-1 provides a summary of cross-cutting needs and the proposed work to address those needs. USED FUEL DISPOSITION CAMPAIGN Gap Analysis to Support Extended Storage of Used Nuclear Fuel Rev. 0 January 31, 2012 vii Table S-1. Summary of Cross-Cutting Needs Cross-Cutting Importance Approach to Need Description of R&D Closing Gap Monitoring Continued efficacy or acceptable performance of High Develop systems dry storage systems for relatively short-term for early detection storage can be demonstrated through accelerated of confinement tests to validate models and analyses. However, boundary for extended storage, projection of continued degradation, efficacy or acceptable performance may not be monitoring cask possible without collecting data to validate the environmental models developed using data from short-term changes, and data tests. To collect the necessary data as part of the transmission R&D program and engineering-scale without demonstration, more effective monitoring compromising cask systems must be developed to detect failures (or or canister precursors to those failures) and to evaluate boundary. materials property changes that can be correlated to their structural performance. Medium Develop systems for early detection of corrosion of metal reinforcement. Temperature Most degradation mechanisms are temperature- High Calculate Profiles dependent with rates generally increasing with temperature profiles temperature. Current safety analyses are of SSCs as a appropriately based on bounding temperature function of time for profiles, but recent data has shown that high representative dry burn up cladding can become brittle at lower cask storage temperatures due to phenomena such as radial systems. hydride precipitation. Similarly,